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Sex Development Flashcards

1
Q

What does sex chromosome aneuploidy mean?

A

Refers to disorders where the affected person doesn’t have the normal number of X or Y chromosomes

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2
Q

What is the genotype of Turner Syndrome?

A

45; X (or 45; XO)

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3
Q

What are the signs at birth of Turner Syndrome?

A

Prenatal cystic hygroma; webbed neck; puffy hands & feet; heart defects like coarctation of the aorta

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4
Q

What are other signs of Turner Syndrome?

A

Short stature; normal intelligence; infertility due to non-functioning ovaries; hormone dysfunction; low set ears; broad chest. Occurs in 1/2500 newborn girls

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5
Q

What is the genotype of Kleinfelter Syndrome?

A

47; XXY

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6
Q

Typical Kleinfelter Syndrome presentation

A

Tall stature; small testes; infertility; hypospadias; gynecomastia; learning disabilities; delayed speech. Occurs in 1/500 - 1/1000 newborn boys

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7
Q

What is the genotype of boys with Jacobs Syndrome?

A

47; XYY

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8
Q

Typical Jacobs Syndrome presentation

A

Learning disabilities; speech/developmental delays; behavioral/emotional difficulties; Autism spectrum; tall stature. Occurs in 1/1000 newborn boys

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9
Q

Genotype of Triple X Syndrome

A

47; XXX

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10
Q

Typical presentation of Triple X Syndrome

A

May be tall; increased risk of learning disabilities; delayed speech/motor; seizures; kidney abnormalities. Occurs in 1/1000 newborn girls

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11
Q

What determines secondary sex characteristics?

A

Gonadal development

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12
Q

What happens in males in the 7th week of conception?

A

Differentiation of genital ridge

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13
Q

In males; what does the genital ridge differentiate into?

A

Sertoli cells and Leydig cells

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14
Q

In the 8th week; what do Leydig cells begin to produce?

A

Testosterone

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15
Q

In the 8th week; what do Sertoli cells begin to produce?

A

Anti-Mullerian Hormone (AMH)

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16
Q

In males; what do the primitive sex cords differentiate into? (in the 8th week)

A

Testis cords & rete testis (eventually become seminipherous tubules during puberty)

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17
Q

What prompts the body to begin developing female human reproductive organs around the 7th-8th week?

A

Absense of SRY & presence of 2X chromosomes

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18
Q

In females; what do the Primitive sex cords dissociate into?

A

Irregular clusters

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19
Q

What happens to the medullary (primitive) cords in females?

A

They cords regress and cortical (secondary) cords are formed

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20
Q

What is the destiny of the cortical cords in females?

A

Destined to become follicular cells of the ovary (Follicular cells will eventually surround an oogonium which together are the primary ovarian follicle).

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21
Q

What are the 2 pairs of genital ducts that are initially present in both males and females?

A

Mesonephric (Wolffian) ducts and Paramesonephric (Mullerian) ducts

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22
Q

Male structures are derived from which ducts?

A

Mesonephric (Wolffian) ducts

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23
Q

Which two genes are responsible for the body choosing the Mesonephric (Wolffian) ducts during development? Are these genes autosomal or sex-linked?

A

SRY gene (on the Y chromosome) & SOX9 gene (This is autosomal gene)

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24
Q

What is the function of SRY and SOX9 genes?

A

They are both transcription factors; responsible for production of Anti-Mullerian Horomone (AMH; aka Mullerian inhibitory Substance - MIS)

25
What does AMH (aka MIS) do?
Causes regression of the paramesonephric duct
26
What does the gene FGF9 (fibroblast growth factor 9) do?
A protein coding gene; produces a chemotactic factor that causes tubules from mesonephric duct to penetrate the gonadal ridge. This is essential for differentiation of the testis.
27
What do the SF1/NR5A1 genes do?
Stimulates differentiation of the Sertoli & Leydic cells
28
Under the influence of testosterone; what do the mesonephric ducts elongate to form?
Epidymis; Seminal Vesicles; Vas Deferens
29
What does the WNT4 protein do in relation to the Paramesonephric (Mullerian) Ducts?
Extracellular signaling factor responsible for differentiation of the ovary
30
What inhibits WNT4 protein?
SOX9
31
What does the DHH gene do in female development?
Produces a nuclear hormone receptor.
32
What up-regulated DHH gene? What does it downregulate?
Up-regulated by WNT4; Downregulates SOX9
33
What does the RSPO1 gene do?
It is a Coactivator of the WNT pathway
34
Under the influence of ESTROGEN (from maternal and placental sources); what structures are formed from the Paramesonephric (Mullerian) Ducts?
uterus; cervix; broad ligament; fallopian tubes; upper 1/3 of the vagina
35
Where do both sets of external genitalia orginate?
Urogenital sinus
36
What causes male external structures to develop from urogenital sinus?
Androgen (dihydrotestosterone) exposure from the testis
37
What influence does androgen exposure have on the external genitalia?
Prompts development of penis; scrotum; and the location of the urethral opening at the tip of the penis
38
What causes female external genitalia to develop from the urogenital sinus?
Estrogen exposure from maternal and placental sources (aka lack of androgen production)
39
What influence does estrogen exposure have on the external genitalia?
Prompts development of clitoris; labia majora and minora; and lower 2/3 of vagina
40
What is the overall pathway of sex development? What determines gonads/2ndary sexual characteristics/external genitalia?
Chromosomes determine gonad development; gonads determine external genitalia & secondary sexual characteristics
41
What is the name/rankings for sexual differntiation?
Prader scale - rated between 'no virilization' to stage 5 (fully male)
42
If a baby is born with ambiguous genitalia; which 5 things should the clinician do on the 1st day of life?
1 - obtain FISH studies for Sex Chromosomes & a karyotype or chromosomal microarray 2 - Order hormone studies (LH; FSH; Testosterone; Dihydrotestosterone; +/- AMH) 3 - Consider ultrasound study (check for gonads/uterus) 4 - Surgical consult with urology 5 - Consider consult with specialized team; if available (endocrinology; genetics; urology; psychology)
43
What do you consider if the baby is 46; XY DSD BUT testosterone and dihydrotestosterone are normal or elevated?
Androgen Insensitivity Syndrome (AIS) or 5-alpha reductase deficiency
44
What do you consider if the baby is 46; XY DSD and testosterone and dihydrotestosterone are low?
WT1 associated diseases (Frasier Syndrome or Denys-Drash); SRY mutations or deletions; DHH mutations; RSP01 mutations
45
What do you consider if the baby is 46; XX DSD and testosterone and dihydrotestosterone are low?
Congenital Adrenal Hyperplasia; Ectopic SRY; WNT4 mutations; SOX3 duplications; RSPO1 mutations; MALMD mutations
46
Is the gene responsible for AIS X-linked or Y-linked?
X-linked; AR gene
47
What does mutation in AIS cause? What is the phenotype range?
Even though the body makes androgens (testosterone); it doesn’t necessarily recognize or respond to it. Phenotypes range from mild under-virilization (Partial AIS) to full sex reversal (Complete AIS)
48
What does mutation in 5-Alpha Reductase Deficiency cause? What is the phenotype range?
Mutation causes decreased ability of the body to convert testosterone to dihydrotestosterone. Phenotype shows undervirilized male with increased virilization at the time of puberty
49
Are disorders associated with the SRY gene X-linked or Y-linked?
Y-linked
50
What does deletion or absense of the SRY gene cause?
Full 46; XY sex reversal and a phenotypically normal female
51
What does the ectopic presence of the SRY gene in a 46; XX individual result in?
Phenotypically normal male
52
What do mutations in the SRY gene in a 46; XY individual results in?
Decreased or absent production of Anti Mullerian hormone & under virilization of a male
53
What does the WT1 gene do?
transcription factor for SRY gene
54
What causes Denys-Drash & Frasier Syndromes?
Mutations in the WT1 gene
55
What are the sexual effects of Denys-Drash & Frasier Syndrome?
Sex reversal with 46; XY
56
What are the other health effects with Denys-Drash & Frasier Syndromes?
Both cause different types of chronic kidney disease (diffuse mesangial sclerosis; focal segmental glomerulosclerosis). Increased risk for Wilms Tumor
57
What are the effects of Congenital Adrenal Hyperplasia?
Ambiguous genitalia in 46; XX
58
What causes Congenital Adrenal Hyperplasia?
21-hydroxylase deficiency (usually)
59
What else complicates CAH?
salt wasting in the first few weeks of life and with times of metabolic stress (Decreased sodium and chloride; Increased potassium)

M2M Week3 (5 decks)

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